The present invention relates to a method and an apparatus for removing extraneous matter from waste glass for the reuse of the waste glass as cullet.
Collected waste glass contains caps and the like of glass bottles, synthetic resin lids or covers for cup-shaped glass containers, aluminum caps for liquor bottles and aluminum rings separated from the caps. Waste glass may further contain empty cans for beverages. In recent years, many of caps are made of aluminum, while some are made of iron, synthetic resin, cork, etc. Empty cans are generally aluminum and iron cans. When waste glass containing such extraneous matter is used as cullet, the glass product obtained contains bubbles and unmelted substances, i.e. so-called "stones," and involves changes in color or transparency due to the presence of the extraneous matter. These objections reduce the strength and appearance of the product, seriously impairing the commercial value of the product.
Accordingly the extraneous matter must be removed to the greatest possible extent. However, the extraneous matter varies greatly in shape and properties. Moreover, regardless of whether the waste glass has been fractured or not, some kinds of extraneous matter may not differ from the waste glass in shape, size or specific gravity. Thus, with the exception of magnetic materials which are magnetically separable and empty cans which can easily be separated off, the undesirable matter is not readily separable by the conventional method, such as screening or sink and float separation, which separates the extraneous matter from the waste glass based on the differences therebetween in respect of only one of the kind of material, shape, size and specific gravity. In fact, the conventional methods give very low yields. For this reason, very cumbersome procedures are usually followed which involve various kinds of separation methods including the final step of manual separation. However, the manual separation is not fully efficient in removing the extraneous matter which remains to be separated off. Consequently, the waste glass resulting from the separating operation still contains a considerable amount of extraneous matter.